When weather conditions obscure the visibility of a landing, the runway lights are no longer visible; or, if visible, the distance of visibility is so restricted as to make their use of limited, and hence unreliable, value. This invention relates to a navigational system in which the pilot has available to him a display simulating runway lights and VASI equipment readout through a CRT. This is presented as a display on the CRT in the present invention, illustrating the runway lights and VASI as they would appear but for obscured vision from weather. In place of the visual light spectrum, which is shielded by fog or other weather conditions, there is displayed on the CRT, simulated lights and VASI.
The CRT is either in the form of a fixed display or heads-up display projected onto the windshield, so what the pilot sees is very similar to, if not precisely the same as, the visible landing light patterns on a runway as they would appear if visible.
The system is characterized by its simplicity in that in place of visible light there is utilized a microwave emitter and reflector antenna which is adapted to generate in conical patterns a series of emitted RF microwaves corresponding to what would otherwise be seen as visible light. On board the aircraft is a camera with a pinhole aperture which converts the received microwave signal to an inverted image on a screen which is positioned according to distance-measuring equipment (DME) to simulate by display size, as well as display location, what the pilot would otherwise observe as a series of visible runway lights. This on-board camera image is then converted to an electrical signal which is transmitted to, and then displayed on, a receiver such as a CRT.
The camera maintains the same parallel orientation through a gimbaled platform, so that regardless of the position of the aircraft, the camera is constantly aimed, and maintains aimed parallel positions, notwithstanding the changing orientation of the aircraft. Because the camera maintains its parallel aimed orientation at all times, the display on the CRT reflects what would be visible as runway ground lights were it not for restricted visibility.
There is presented on the CRT, a "painted" display from three dimensions, even though the CRT has a two-dimensional flat screen.
Other objects and features of the invention will become apparent from a consideration of the following description, which proceeds with reference to the accompanying drawings.